This particular set of marks has always been confusing as it is found with various sets of initials struck at the end, and sometimes with a slight variation with the marks. It may be that of a manufacturer of blanks who was supplying silver platers and marked the pieces with their initials.
The below is the mark of Thomas Wilkinson, the fourth mark being his famous Pelican device. His former manufactory, the Pelican Works, is a well known landmark at Birmingham. Thomas Wilkinson was in business from 1832 until 1932.